Today we are going to Discuss about sensors .
1.What is a sensor?
2. Types of sensors
.IR sensor
.Sound sensor
.Temperature sensor
3. How to use it?
4. Where to use it?
• A sensor is a device that measures a physical
quantity and converts it into a signal which can
be read by an observer or by an instrument.
• Sensors are used in everyday objects such as
touch-sensitive elevator buttons (tactile sensor)
and lamps which dim or brighten by touching the
base.
• Applications include cars, machines, aerospace,
medicine, manufacturing and robotics.
• IR SENSOR
• SOUND SENSOR
• TEMPERATURE SENSOR
• IR sensor works on the principle of
emitting IR rays and receiving the reflected
ray by a receiver (Photo Diode).
• IR source (LED) is used in forward bias.
• IR Receiver (Photodiode) is used in
reverse bias.
• A Comparator is a device which
compares two voltages or currents and
switches its output to indicate which is
larger.
• Comparator is an Op-amp.
Contd....
• The LM35 is an integrated circuit sensor
that can be used to measure temperature
with an electrical output proportional to
the temperature (in oC).
• The scale factor is 10mV/oC .
The 555 Timer IC is an integrated
circuit (chip) implementing a variety
of timer and multi-vibrator applications.
• MONOSTABLE MODE
• BISTABLE MODE
• ASTABLE MODE
• In this mode, the 555 functions as a "oneshot"
• Applications include timers, missing pulse
detection, bouncefree switches, touch
switches, frequency divider, capacitance
measurement, pulse-width modulation
(PWM) etc
Contd....
• The pulse begins when the 555 timer receives a trigger
signal.
• The width of the pulse is determined by the time
constant of an RC network, which consists of
a capacitor (C1) and a resistor (R1).
• The pulse width can be lengthened or shortened to the
need of the specific application by adjusting the values of
R and C.
T = 1.1 X R1 X C1
• In bi-stable mode, the 555 timer acts as a basic flipflop.
• The trigger and reset inputs (pins 2 and 4 respectively
on a 555) are held high via pull-up resisters while the
threshold input (pin 6) is simply grounded.
• Thus configured, pulling the trigger momentarily to
ground acts as a 'set' and transitions the output pin
(pin 3) to Vcc (high state).
• Pulling the reset input to ground acts as a 'reset' and
transitions the output pin to ground (low state).
• No capacitors are required in a bi-stable configuration
• Pin 8 (Vcc) is, of course, tied to Vcc while pin 1 (Gnd)
is grounded.
• Pins 5 and 7 (control and discharge) are left floating.
• In A-stable mode, the '555 timer ' puts out a
continuous stream of rectangular pulses having a
specified frequency.
• Resistor R1 is connected between VCC and the
discharge pin (pin 7) and another resistor (R2) is
connected between the discharge pin (pin 7), and
the trigger (pin 2) and threshold (pin 6) pins that
share a common node.
• Hence the capacitor is charged through R1 and R2,
and discharged only through R2.
Contd....
• In the above circuit we are triggering the 555
timer by applying voltage produced by sound.
• This voltage when generated pass through the
capacitor which works as a filter.
• This filtered voltage is then fed to transistor
which is inverting the voltage and also
amplifying it.
• And hence creating a negative triggering pulse.
Thank You…